You can install multiple USB cameras, then provide mjpeg streams. Very stable (at least on a wired ethernet connection), but limited to supported USB cameras. The logitech ones work well.

I'm also using old/cheap Android phones as wifi streaming devices using this app. Again, provides an MJPEG stream - very stable as long as your phone is happy (some go into meltdown with high CPU over long periods).

Nice little camera and ticks all the boxes. Web interface (though you need a smartphone to get it configure initially), wifi, 1028x768 or 640x352. ONVIF support, and relatively cheap - about £15 delivered.